Category Archives: Research

Technical Report – Operation-based Collaborative Data Sharing for Distributed Systems, Masato Takeichi. November 26, 2021.


Collaborative Data Sharing raises a fundamental issue in distributed systems. Several strategies have been proposed for making shared data consistent between peers in such a way that the shared part of their local data become equal.

Most of the proposals rely on state-based semantics. But this suffers from a lack of descriptiveness in conflict-free features of synchronization required for flexible network connections. Recent applications tend to use non-permanent connection with mobile devices or allow temporary breakaways from the system, for example.

To settle ourselves in conflict-free data sharing, we propose a novel scheme Operation-based Collaborative Data Sharing that enables conflict-free strategies for synchronization based on operational semantics.

TR-OCDS (Click to download)

Also available at

Technical Report – Conflict-free Collaborative Set Sharing for Distributed Systems, Masato Takeichi. November 19, 2021.


Collaborative Data Sharing is widely noticed to be essential for distributed systems.
Among several proposed strategies, conflict-free techniques are considered useful for serverless concurrent systems.

They aim at making shared data be consistent between peers in such a way that their local data do not become equal at once, but they arrive at the same data eventually when no updates occur in any peer.

Although the  Conflict-free Replicated Data Type (CRDT) approach could be used in data sharing as well, it puts restrictions on available operations so as to concurrent updates never cause conflicts. Even for sets, popular operations such as insertion and deletion
are not freely used, for example.

We propose a novel scheme for  Conflict-free Collaborative Set Sharing that allows both insertion and deletion operations. It will provide a new synchronization method for data sharing and gives a fresh insight into designing conflict-free replicated data types. We might consider that this becomes a substitute for CRDTs.

TR-CCSS (Click to download)

Also available at

Technical Report – BCDS Agent: An Architecture for Bidirectional Collaborative Data Sharing, Masato Takeichi. March 31, 2020.


We have been discussing data sharing among autonomous independent sites in the distributed system to meet various demands for application. Among them the need for collaborative data sharing has attracted attention in many fields where not only the owner of the original data but the receiver can update that shared data. The BCDS Agent is a new building unit for configuring such systems with scalability and versatility. It rests on the novel feature of bidirectional programming which encourages us to take the compositional approach in developing the distributed system with data consistency.
We present the key issue on designing the BCDS Agent with some examples.


Published version (August 2021) available at